ACTIVITY OF MONKEY FRONTAL EYE FIELD NEURONS PROJECTING TO OCULOMOTOR REGIONS OF THE PONS
ACTIVITY OF MONKEY FRONTAL EYE FIELD NEURONS PROJECTING TO OCULOMOTOR REGIONS OF THE PONS
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DOI：
10.1152/jn.1992.68.6.1967
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发表时间：
1992-12-01
影响因子：
2.5
通讯作者：
SEGRAVES, MA
中科院分区：
文献类型：
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作者：
SEGRAVES, MA
1. 本研究在恒河猴的额视野中发现了投射到脑桥动眼区的神经元，并表征了这些神经元从额视野到脑桥的信号。在两只有行为的恒河猴身上，通过一个尖端位于或靠近脑桥全顶区的刺激微电极的反向激发，识别了投射到脑桥的额叶视野神经元。该刺激部位与中缝间核（RIP）相对应。此外，电刺激额眼野被用来证明额眼野输入对全顶区和周围旁脉桥状网状结构（PPRF）神经元的影响。鉴定并表征了25个皮质孔顶神经元。大多数投射到脑桥的额叶视野神经元要么是运动神经元，与眼跳运动相关（48%），要么是响应中央凹视觉刺激与注视相关活动（28%）的中央凹神经元。皮质孔蛋的运动神经元在受限运动领域内进行扫视之前、期间和之后都被激活。所鉴定的皮质孔区神经元的活动与上丘反方向兴奋的神经元的活动非常相似，其中59%具有运动相关活动，22%具有中央凹和固定相关活动。高强度，短时间的电刺激额眼野导致全顶神经元停止放电。放电的停止似乎是立即的，在小于或等于5毫秒的时间内。综合顶神经元的静止时间取决于皮层刺激的强度，在1000 μ a强度下连续3次刺激脉冲，持续时间为6 ms，最长可达30 ms。低强度、持续时间较长的电刺激（24脉冲，75 μ a， 70毫秒）通常用于唤起额叶视野的扫视，但在此之后，全顶神经元的放电也会停止，但仅在延迟约30毫秒之后。对于这些刺激，当刺激被关闭时，全顶神经元恢复放电。同样的刺激导致全能顶神经元停止发射PPRF中兴奋的爆发神经元。激发潜伏期在4.2 ~ 9.8 ms之间，表明在ppr1的额叶视野神经元和爆发神经元之间至少有一个额外的神经元。本研究通过使用逆行和顺行示踪剂证实并扩展了先前工作的结果，证明了从额部视野到脑桥的直接投影。这条直接通路使额叶视野短潜伏期进入距动眼肌神经元仅几个突触的动眼肌中枢。额叶视野与上丘和脑桥平行发送与运动相关的信息。这个信息提供了即将到来的眼跳的幅度和方向（在哪里）以及眼跳开始前的固定维持和释放（何时）的信息。
1. This study identified neurons in the rhesus monkey's frontal eye field that projected to oculomotor regions of the pons and characterized the signals sent by these neurons from frontal eye field to pons.2. In two behaving rhesus monkeys, frontal eye field neurons projecting to the pons were identified via antidromic excitation by a stimulating microelectrode whose tip was centered in or near the omnipause region of the pontine raphe. This stimulation site corresponded to the nucleus raphe interpositus (RIP). In addition, electrical stimulation of the frontal eye field was used to demonstrate the effects of frontal eye field input on neurons in the omnipause region and surrounding paramedian pontine reticular formation (PPRF).3. Twenty-five corticopontine neurons were identified and characterized. Most frontal eye field neurons projecting to the pons were either movement neurons, firing in association with saccadic eye movements (48%), or foveal neurons responsive to visual stimulation of the fovea combined with activity related to fixation (28%). Corticopontine movement neurons fired before, during, and after saccades made within a restricted movement field.4. The activity of identified corticopontine neurons was very similar to the activity of neurons antidromically excited from the superior colliculus where 59% had movement related activity, and 22% had foveal and fixation related activity.5. High-intensity, short-duration electrical stimulation of the frontal eye field caused omnipause neurons to stop firing. The cessation in firing appeared to be immediate, within less-than-or-equal-to 5 ms. The time that the omnipause neuron remained quiet depended on the intensity of the cortical stimulus and lasted up to 30 ms after a train of three stimulus pulses lasting a total of 6 ms at an intensity of 1,000 muA. Low-intensity, longer duration electrical stimuli (24 pulses, 75 muA, 70 ms) traditionally used to evoke saccades from the frontal eye field were also followed by a cessation in omnipause neuron firing, but only after a delay of approximately 30 ms. For these stimuli, the omnipause neuron resumed firing when the stimulus was turned off.6. The same stimuli that caused omnipause neurons to stop firing excited burst neurons in the PPRF. The latency to excitation ranged from 4.2 to 9.8 ms, suggesting that there is at least one additional neuron between frontal eye field neurons and burst neurons in the PPRF.7. The present study confirms and extends the results of previous work, with the use of retrograde and anterograde tracers, demonstrating direct projections from the frontal eye field to the pons. This direct pathway gives the frontal eye field short-latency access to oculomotor centers just a few synapses away from oculomotoneurons.8. The frontal eye field sends a movement-related message in parallel to the superior colliculus and the pons. This message provides information about the amplitude and direction of impending saccades (where) and about both the maintenance of fixation and the release of fixation before the beginning of a saccade (when).